ngx translate custom loader

translate.loader.ts

/*
*	Custom Translate Loader to reload lang JSON on network failure
*/

import { TranslateLoader } from "@ngx-translate/core";
import { Injectable } from "@angular/core";
import { HttpHeaders, HttpClient } from "@angular/common/http";
import { ConnectionService } from ".";
import { Observable } from "rxjs";
import { filter, take } from "rxjs/operators";

@Injectable()
export class CustomTranslateLoader implements TranslateLoader {
	private contentHeader = new HttpHeaders({ "Content-Type": "application/json", "Access-Control-Allow-Origin": "*" });
	constructor(private http: HttpClient, private connectionService: ConnectionService) {
	}
	getTranslation(lang: string): Observable<any> {
		const apiAddress = "/locale/" + lang + ".json";
		const callJSON = (observer) => {
			this.connectionService.monitor()
				.pipe(filter((isConnected: any) => isConnected), take(1))
				.subscribe(() => {
					this.http.get(apiAddress, { headers: this.contentHeader })
						.subscribe((res: Response) => {
							observer.next(res);
							observer.complete();
						}, (error) => {
							callJSON(observer);
						});
				});
		}

		return Observable.create(observer => {
			this.http.get(apiAddress, { headers: this.contentHeader })
				.subscribe((res: Response) => {
					observer.next(res);
					observer.complete();
				}, (error) => {
					callJSON(observer);
				});
		});
	}
}